Today, America's fluid transport companies rely on rail tank cars for routine, safe, efficient, cost effective handling of some of the most corrosive and volatile chemicals and gases, such as chlorine or liquefied petroleum gas (LPG), as well as general service products, such as alcohol, polymers, corn syrup and the like. Railroad tank cars have served an important role in the shaping of many industries.
In the late 1800's Standard Oil dominated one such industry by gaining control of oil shipping using railroad tank cars as a “secret weapon.” At the time, oil refined into kerosene was in big demand for lighting and other household and business uses. The earliest tank cars were built in 1865 to transport the oil from field wells to the refineries. Although the cars were little more than two large wooden tubs mounted on a flatcar, they were much more efficient than previous shipping options. And within five years, an improved design using the now-familiar cylindrical iron tanks made tank cars the obvious transportation choice.
Nonetheless, tank car design continued to evolve. Shortly after the turn of the century, cars with iron tanks banded onto wooden underframes were replaced by steel “X-car” (named for the shape of its underframe), which connected the tank to an underframe with a specially-created anchor to keep the tank from shifting. The durable X-car permitted new commodities such as gasoline and chemicals to be shipped more safely. Heater pipes, opened tank car shipping to products such as paraffin and asphalt.
During the 1920s, new markets emerged for chemicals, liquefied gas and foods. And the explosion in auto ownership increased the oil industry itself far beyond anything previously experienced. It wasn't long, however, before the collapse of the nation's economy in the Depression of the early 1930s, caused the number of surplus tank cars to increase dramatically. Thousands of tank cars were repurchased from customers by manufacturers who eventually leased them out as business recovered, launching a trend that continues today.
Innovations in a new fusion welding process led to increased tank strength, and as a result various products were able to be shipped under high pressure. When World War II broke out, the threat of enemy submarines kept oil tankers off the seas, and tank cars became crucial to the wartime effort. Nearly 15,000 retired tank cars were sent to repair shops, where they were refurbished to haul oil in government-run unit trains.
When the war ended, the tank cars' dominant role in transporting bulk liquids was increasingly threatened by the growth of both oil pipelines and long-haul trucking. In response to this competitive threat, an all-out effort to serve producers in emerging markets such as petrochemicals and fertilizers was launched.
In 1954 a revolutionary new domeless tank car without an underframe was unveiled. An underframeless car had been designed back in the early 1900s, but it was rejected then as unsafe. However, engineers now felt that the tank arrangement actually improved the overall strength of the car. They also proved that the top dome, long considered necessary to hold product expansion during shipping, could be eliminated simply by filling the tank slightly less than full.
Government and industry standards soon set tank car load limits based on one of either a 2% outage point—a percentage of the tank car's volume required to remain empty—or the maximum gross weight of the tank car, including contents. For companies filing tank cars, and paying based on the number of tank cars used, filling each car as full as allowable is imperative to cost effectiveness. However, until the present invention, it was difficult to accurately estimate the full level point of a tank car due to factors such as temperature fluctuations, varied tank car configurations, changing flow rates, and the like.
Thus, there is a need, generally, for a system which assists in controlling and monitoring tank car loading while achieving maximum usage of tank volume or weight limits. Specifically, a need exists for a system which provides monitoring and control of the filling process automatically and, in some cases, remotely.